For nucleic acid analysis to answer human genomic questions, e.g. in white blood cells from whole blood, the cells must firstly be broken up in a sample preparation step and the DNAs thereby released must subsequently be isolated. It is in this case necessary to remove blood constituents such as hemoglobin, immunoglobulins and lactoferrin, which could inhibit a subsequent PCR.
In the laboratory, these working steps are carried out according to a sufficiently well-known prior art. Besides other methods, for example, cells can be broken up (so-called lysis) with an alkaline solution (NaOH) and the DNAs can subsequently be bound to silica-coated magnet beads. By applying a magnetic field, the magnet beads laden with DNA are fixed and washed. The DNA isolated in this way can subsequently be used with or without beads for a PCR (Polymerase Chain Reaction).
In the prior art, the DNA-binding magnet beads are used as a suspension in a cell lysis buffer. All the working steps are carried out for example in 1.5 ml reaction vessels (so-called “Eppendorf” vessels). For example, 10 μl of whole blood is added to a predetermined volume of the bead suspension (e.g. 200 μl). The blood cells are thereby disintegrated and the DNAs are released. The magnet beads bind the DNA and form a DNA/bead complex. Such a DNA/bead complex can subsequently be fixed by a magnetic field on the vessel wall of the Eppendorf tuber, so that washing steps can be carried out to remove PCR-inhibiting substances. The PCR can subsequently be carried out.
Conduct of the latter method is contingent on the provision of laboratory equipment such as the “Eppendorf” vessels (tubes), tube holding devices including magnets, pipetting equipment, cooling containers for reagents, and must be carried out by trained personnel while complying with safety rules (infection risk, waste disposal, etc.). A plurality of volumetric and highly accurate dosings of substances which are sometimes hazardous to health (e.g. NaOH) first be carried out by pipetting. These working steps are also time-consuming.
US 2002/0022261 A1 has already disclosed systems for miniaturized genetic analysis and associated operating methods, in which a cartridge with at least one input and a porous passage, which is intended to have DNA-binding properties, is used. Disintegration of cells takes place, to which end reagents are provided optionally on the vessel wall. Structured regions of the wall may furthermore be coated with DNA-binding materials, optionally also magnet beads. Overall a series of different proposals are provided there in order to perform the measurement for the genetic analysis, although a continuous method is still not carried out. A mixture for the isolation of DNA is furthermore known from EP 0 723 549 B1, this mixture especially containing silica gel, glass particles and at least one chaotropic salt.
Furthermore, WO 99/33559 A describes a device for separating and analyte from a fluid sample, which comprises the cartridge with a lysation chamber in the sample flow path, the cells of the sample being filtered out via a filter and disintegrated. The analyte separated in this way is fed to individual sensor chambers in the device for analysis.